############################################################
#                                                          #
# The implementation of PHPRPC Protocol 3.0                #
#                                                          #
# xxtea.py                                                 #
#                                                          #
# Release 3.0.1                                            #
# Copyright (c) 2005-2008 by Team-PHPRPC                   #
#                                                          #
# WebSite:  http://www.phprpc.org/                         #
#           http://www.phprpc.net/                         #
#           http://www.phprpc.com/                         #
#           http://sourceforge.net/projects/php-rpc/       #
#                                                          #
# Authors:  Ma Bingyao <andot@ujn.edu.cn>                  #
#                                                          #
# This file may be distributed and/or modified under the   #
# terms of the GNU Lesser General Public License (LGPL)    #
# version 3.0 as published by the Free Software Foundation #
# and appearing in the included file LICENSE.              #
#                                                          #
############################################################
#
# XXTEA encryption arithmetic library.
#
# Copyright (C) 2005-2008 Ma Bingyao <andot@ujn.edu.cn>
# Version: 1.0
# LastModified: Oct 5, 2008
# This library is free.  You can redistribute it and/or modify it.

import struct

_DELTA = 0x9E3779B9

def _long2str(v, w):
    n = (len(v) - 1) << 2
    if w:
        m = v[-1]
        if (m < n - 3) or (m > n): return ''
        n = m
    s = struct.pack('<%iL' % len(v), *v)
    return s[0:n] if w else s

def _str2long(s, w):
    n = len(s)
    m = (4 - (n & 3) & 3) + n
    s = s.ljust(m, "\0")
    v = list(struct.unpack('<%iL' % (m >> 2), s))
    if w: v.append(n)
    return v

def encrypt(str, key):
    if str == '': return str
    v = _str2long(str, True)
    k = _str2long(key.ljust(16, "\0"), False)
    n = len(v) - 1
    z = v[n]
    y = v[0]
    sum = 0
    q = 6 + 52 // (n + 1)
    while q > 0:
        sum = (sum + _DELTA) & 0xffffffff
        e = sum >> 2 & 3
        for p in xrange(n):
            y = v[p + 1]
            v[p] = (v[p] + ((z >> 5 ^ y << 2) + (y >> 3 ^ z << 4) ^ (sum ^ y) + (k[p & 3 ^ e] ^ z))) & 0xffffffff
            z = v[p]
        y = v[0]
        v[n] = (v[n] + ((z >> 5 ^ y << 2) + (y >> 3 ^ z << 4) ^ (sum ^ y) + (k[n & 3 ^ e] ^ z))) & 0xffffffff
        z = v[n]
        q -= 1
    return _long2str(v, False)

def decrypt(str, key):
    if str == '': return str
    v = _str2long(str, False)
    k = _str2long(key.ljust(16, "\0"), False)
    n = len(v) - 1
    z = v[n]
    y = v[0]
    q = 6 + 52 // (n + 1)
    sum = (q * _DELTA) & 0xffffffff
    while (sum != 0):
        e = sum >> 2 & 3
        for p in xrange(n, 0, -1):
            z = v[p - 1]
            v[p] = (v[p] - ((z >> 5 ^ y << 2) + (y >> 3 ^ z << 4) ^ (sum ^ y) + (k[p & 3 ^ e] ^ z))) & 0xffffffff
            y = v[p]
        z = v[n]
        v[0] = (v[0] - ((z >> 5 ^ y << 2) + (y >> 3 ^ z << 4) ^ (sum ^ y) + (k[0 & 3 ^ e] ^ z))) & 0xffffffff
        y = v[0]
        sum = (sum - _DELTA) & 0xffffffff
    return _long2str(v, True)

if __name__ == "__main__":
    print decrypt(encrypt('Hello XXTEA!', '16bytelongstring'), '16bytelongstring')
